1. Field of the Invention
The present invention relates to the field of display techniques, and in particular to a gate driver on array circuit.
2. The Related Arts
Liquid crystal display (LCD) has many advantages of thin body, energy saving, and no radiation, which has been widely used. The existing LCD in the market is mostly backlight LCD, which comprises liquid crystal panel and backlight module. The working principle of the liquid panel is to provide liquid crystal molecules between two parallel glass substrates, and to provide driving voltage on the two glass substrates to control the rotating direction of the liquid crystal molecules, so that the light from the backlight module is refracted and generates the picture.
Recently, the development of LCD tends to high integration and low costs. A very important technology is gate drive on array (GOA) mass production technology, which uses gate drive on array technology to integrate the gate switching circuits on the array substrate of the liquid crystal panel, acting as shift register, so that the gate driver IC can be saved and then reduces the product costs from material costs and process steps.
The purpose of the gate driver on array circuit is to output the scanning waveform output from the integrated circuit through circuit operation, so that the pixel switch is turned on, and then input the data signal to the indium tin oxide (ITO) conducting electrode. After inputting the data signal, hold the data signal until the next frame is turned on. During the circuit operation, the turning off (holding) time of the scanning circuit is much longer than the scanning time. Referring to FIG. 1, assuming the resolution is 1366×768, the turning on time of a scanning circuit is 2.17 μs, and the scanning time of one frame is 16.67 ms (60 Hz). Because a scanning circuit is turned off in the remaining time of one frame after turning on, the requirement of stability characteristics of the thin film transistor (TFT) in the gate driver on array circuit is very high in this time. However, one driver circuit comprises more than ten thin film transistors, and it is difficult to keep each thin film transistor having stable switching characteristics during actual semiconductor manufacturing process. Therefore, the important thin film transistor (such as thin film transistor in each driver circuit output terminal) in the driver circuit requires fairly good switching characteristics
Each conventional driver circuit only has one Vss signal. When the driver circuit is turned off, the voltage difference Vgs between the gate and the source of the thin film transistor at the output terminal is 0V. Referring to FIG. 2, it is I-V curve of thin film transistor. It can be known that the current flowing through the thin film transistor is still in the linear region when Vgs is 0V. The leakage current of the thin film transistor is relatively large, which is hard to control precisely and not good for display quality of the LCD.